270 ELEMENTARY BIOLOGY. [CHAP. 



a. The ripe ova, large round bodies completely 

 filling the pointed extremity of the saccular 

 ovary. A granular vttellus, a large round ger- 

 minal vesicle and a vitelline membrane will be 

 observed for each. 



/?. The immature ova. Work towards the base of 

 the ovary the ova decrease in size and become 

 more numerous. The younger of them are 

 destitute of a vitelline membrane. Work back 

 towards the attached end, and note graduating 

 into ft as (3 does into a 



y. the germinal epithelium, a solid mass of small 

 undifferentiated cells filling the base of the 

 ovary. 



j. Remove a small portion of a testis of the youngest 

 worm obtainable, crush and examine in eosin under 

 a high power. Note the cells of the germinal epi- 

 thelium, irregular in shape, each with a large central 

 nucleus and a single nucleolus. 



k. Tease up in a similar manner a small portion of 

 one of the seminal vesicles of an older animal. 

 Treat with acetic acid and magenta spermatozoa 

 in all stages of development will be seen. Look 

 for the following 



a. Cells of the germinal epithelium identical with 

 j. They are sometimes to be found only with 

 difficulty. 



/?. The same during the early maturation stages 

 conspicuous as the predominant mulberry-like 

 masses. Focus to the surface of one of these 

 and work through it. It consists of a large pro- 

 toplasmic body, differentiated peripherally into 



